[libav-api] Cannot open stream

Manuel Torres manuel.torres.fernandez at gmail.com
Tue Jun 10 18:17:50 CEST 2014


I have to admit that I barely understood that reply so I assume that I am
missing something big and obvious.

Answers to the questions:
"Are you aware that the sprop-parameter-sets contain the sps and pps nal
packets encoded in base64?"
I think that the answer would be no because I do not know what those are
but I will look it up.

"Is your code looking for the sps and pps nals in the rtp stream itself?"
Hard to say. The library is doing everything for me. I have no clue of what
is going on there. I set up the context, open the input, set up the codec
and grab the frames. Nothing more advanced than that.

"Are you accounting for whether or not the sps and pps are coming in-stream
vs in the sdp?"
I guess I am not. I do not even know how to get the data from the SDP. I
will look it up too but I would appreciate if anybody could tell me.

"If your rtp reception code can produce an h264 annex b file, can vlc play
it?"
I suppose you are referring to the Annex B of the H.264 specification. I
have not read the specification but I have a copy of it so I will check
that annex and try to create that file to test as described.


Regardless of my answers to those questions, I understand from the reply
that the data is there somewhere. I would be really grateful if someone
could tell me where to find it in the library structures and, if it is not
too much to ask, a link to how to parse "the sps and pps nal packets",
whatever those are. Base64 is the only thing I understood from that first
question. Shame on me.



On Tue, Jun 10, 2014 at 5:28 PM, Joshua Kordani <jkordani at lsa2.com> wrote:

> Are you aware that the sprop-parameter-sets contain the sps and pps nal
> packets encoded in base64?  Is your code looking for the sps and pps nals
> in the rtp stream itself?  Are you accounting for whether or not the sps
> and pps are coming in-stream vs in the sdp?
>
> If your rtp reception code can produce an h264 annex b file, can vlc play
> it?   Making your code create this file will tell you that you have
> everything you need in order to pass data to the decoding library.  If vlc
> can play the h264 annex b that you create, then you know that all you have
> left to do is figure out how to pass this data to the library to decode it
> yourself, most likely.
>
> Joshua Kordani
> LSA Autonomy
>
>
> On 6/10/14 8:11 AM, Manuel Torres wrote:
>
>> Captured with Wireshark:
>>
>> v=0
>> o=- 1293840088672 1293840088672 IN IP4 192.168.2.93
>> s=Live
>> t=0 0
>> m=audio 0 RTP/AVP 0
>> c=IN IP4 192.168.2.93
>> a=control:rtsp://192.168.2.93/defaultPrimary/mic0/trackID=1
>> m=video 0 RTP/AVP 96
>> c=IN IP4 192.168.2.93
>> a=control:rtsp://192.168.2.93/defaultPrimary/cam0/trackID=1
>> a=fmtp:96 packetization-mode=0; profile-level-id=42A01E;
>> sprop-parameter-sets=J01AH42NKBaHt/4AQAA21BgYGQAAAwPoAADDUOhAB08A
>> AQcau8uNCADp4AAg41d5cE+iwA==,KO48gA==
>> a=rtpmap:96 H264/90000
>> a=x-avg-params:96 source-height=1080; source-width=1920
>> m=application 0 RTP/AVP 98
>> c=IN IP4 192.168.2.93
>> a=control:rtsp://192.168.2.93/defaultPrimary/metadata/trackID=1
>> a=rtpmap:98 vnd.onvif.metadata/90000
>>
>>
>>
>> On Tue, Jun 10, 2014 at 12:58 PM, Luca Barbato <lu_zero at gentoo.org>
>> wrote:
>>
>>  On 10/06/14 12:44, Manuel Torres wrote:
>>>
>>>> Would there be any other way to get the missing data? I guess that there
>>>> must be a way since VLC and MPlayer open the stream.
>>>>
>>>>  Could you please provide the sdp?
>>>
>>> lu
>>>
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>
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